Bem, a melhor taxa é no mercado negro, que existe. No entanto, isso é ilegal. Sua melhor aposta é um banco, e todos os bancos na Etiópia têm as mesmas taxas.
De Wikitravel :
Any commercial bank in Ethiopia can change cash. The rates are the same everywhere. There are dozens of commercial banks in Addis, including in the Sheraton and Hilton hotels, and in the corner of the baggage claim hall at the airport. Most cities and towns that tourists visit will have at least one commercial bank, except for villages in the Omo valley. US dollars, euros, or British pounds are the best currencies to carry.
It is illegal to change money on the black market and the rates aren't much better than what you can get from the banks.
O Lonely Planet tem um bom artigo sobre os custos do dinheiro na Etiópia.
De acordo com o artigo, para caixas eletrônicos:
Bigger branches of the Dashen Bank in Addis Ababa, Bahir Dar, Gonder and Mekele now have ATMs that accept international visa cards. The service is likely to expand to regional cities and even to other banks quite quickly. Note that Mastercard, Solo, Cirrus or Plus cards do not work in any ATM.
USD ou Euros?
Pessoalmente, quase nunca recebo dinheiro adiantado, exceto quando sei que vai ser complicado no país (por exemplo, o Japão, antes de 11 de setembro instalou caixas eletrônicos onipresentes lá que aceitavam cartões estrangeiros).As with many African countries the US dollar is the preferred foreign currency in Ethiopia and although the euro is growing in popularity not all banks will accept it; therefore you should still pack a wedge of greenbacks.